1. Field of the Invention
This invention is related in general to the field of angioplasty treatment of atherosclerotic vessels in mammalian bodies. In particular, the invention pertains to a procedure for providing immediate blood flow through a blocked vessel following its collapse as a result of a failed angioplasty or stent placement.
2. Description of the Related Art
Angioplasty treatments of body vessels are invasive procedures whereby a catheter is inserted into the vascular system to reach and treat a partial or total occlusion causing reduced blood flow. Most notable is balloon angioplasty, where the distal end of the catheter includes an inflatable balloon that is used to expand the vessel and restore sufficient lumen size to ensure adequate blood flow after removal of the catheter.
This procedure has become very common in treating cardiovascular disease and is normally performed, when possible, as a preferable alternative to coronary bypass surgery. Similarly, the placement of a stent, a cylindrical wire mesh that is expanded in the area of stenosis to open and support a coronary artery, is always preceded by an angioplasty. As well understood in the art, the procedure involves placement of a balloon catheter through the locus of a stenosis, typically in a coronary artery, and inflation of the balloon to press against the material creating the occlusion. Because of the pressure exerted by the balloon, the vessel remains completely obstructed during the procedure, which normally lasts one to two minutes. During this time, blood flow through the vessel is essentially precluded and the heart tissue downstream of the blockage is dangerously deprived of oxygen. Therefore, cardiologists try and limit angioplasty procedures to the minimum time required to restore the stenotic passage to an acceptable size.
Various perfusion angioplasty catheters have been developed to enable the continued supply of blood during angioplasty and avoid the occurrence of ischemia. For example, U.S. Pat. Nos. 4,857,054, 5,746,709, 5,807,331 and 5,833,650 disclose various angioplasty catheters that include perfusion channels to produce blood flow past the stenosis during the angioplasty procedure. Some of these catheters utilize exterior, ex-vivo, pumps to create the pressure gradient necessary for blood flow through the catheter while the balloon is inflated. Others utilize sophisticated in-vivo systems of valves, pumps, and multiple balloons in the distal end of the catheter to control the direction of blood flow. While conceptually advantageous to provide an attractive solution to the problem of angioplasty-induced ischemia, these perfusion angioplasty catheters have met very little acceptance in the medical community. One problem is the increased size of such catheters with respect to conventional angioplasty catheters, which results from the added channels and apparatus required to perform the perfusion function within the lumen of the catheter. Other issues are greater cost and intricacy of use. Thus, most cardiologists continue to utilize conventional angioplasty catheters and strive to limit the time of the procedure as much as possible.
Sometimes, as a result of a coronary angioplasty or a stem placement, the arterial vessel collapses and blood flow to the heart is completely blocked, creating a severe, life-threatening emergency. Standard procedure in such situations requires the immediate performance of coronary bypass surgery. In fact, a patient found in such a predicament is rushed to the operating room in the hope of restoring oxygenation to the heart in time to save his or her life. Unfortunately, that is often not possible because of the time delay involved in reaching the affected artery. This invention is directed at solving this emergency problem.